This application claims the priority of German application 197 50 588.0, filed in Germany on Nov. 17, 1997, the disclosure of which is expressly incorporated by reference herein.
The invention relates to a device for exhaust recycling for an internal combustion engine with an exhaust cooler and with a valve that determines the quantity of recycled exhaust, controllable by an adjusting element.
Recycling of cooled exhaust to an internal combustion engine, especially for lowering diesel emissions, is known from ATZ Automobiltechnische Zeitschrift, Vol. 99 (1997), No. 9 (R. Lutz: "Lowering Diesel Emissions by Recycling Cooled Exhaust"). The exhaust recycling valve (AGR valve) and the exhaust cooler (exhaust heat-transfer device) are parts that are independent of one another, installed at different points in the vehicle, and connected with one another by an exhaust line.
A goal of the invention is to modify a device of the type recited at the outset so that a simplified method of manufacturing is obtained.
This goal is achieved by connecting the exhaust cooler and valve directly together so that they form a module. As a result, a simplified and hence less expensive method of manufacture can be performed since individual previously provided elements can be eliminated. In particular, the gas line between the valve and the exhaust cooler is eliminated, together with the connections required therefor.
In preferred embodiments of the invention, provision is made for the adjusting element to be mounted on a part that is in a heat-conducting relationship with the exhaust cooler. This has the advantage that a cooling effect is exerted on the adjusting element by the exhaust cooler, so that the adjusting element is subjected to less heat stress.
In another embodiment of the invention, provision is made such that the adjusting element is mounted on a part provided with one or more channels for a liquid coolant. This produces the advantage that the valve and especially its adjusting element are cooled actively.
Both embodiments allow the valve to be mounted on the exhaust supply side of the exhaust cooler. Mounting the valve on the supply side of the exhaust cooler, i.e. on the side at which the hot exhaust enters, has the advantage that there is a relatively small danger of residues from the exhaust adhering to the valve and its valve elements. This danger, which is even greater when the valve is located downstream from the exhaust cooler, means that adjusting elements with relatively high adjusting forces must be provided which can reliably overcome any jamming of the valve elements caused by deposits of exhaust residues. When it is mounted on the exhaust supply side, the danger of deposits composed of exhaust residues is much less. On the other hand, there is still the danger with this arrangement that the adjusting elements, especially electrical adjusting elements, will be subjected to excessive heat stress. This thermal overloading is offset by the fact that the adjusting element is mounted on a part whose temperature is significantly less than the temperature of the exhaust coming from the internal combustion engine.
In certain preferred embodiments of the invention, provision is made such that the channel or channels of the part that supports the positioning element is/are connected to a coolant supply to the exhaust cooler. Further simplification can be achieved in this manner, since no external connecting lines need be provided between the channels that serve for cooling of the part that supports the positioning element and the exhaust cooler.
In certain preferred embodiments of the invention, provision is made such that the exhaust cooler has an elongate form and that the adjusting element is arranged essentially parallel next to the exhaust cooler. This results in a compact design that can be accommodated relatively simply in a vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.